JP7635082B2 - Heat Recovery System - Google Patents

Description

The present invention relates to a heat recovery system.

There is known a heat recovery system (exhaust heat recovery device) that recovers exhaust heat from an internal combustion engine and supplies the recovered heat to a facility that utilizes the heat (see, for example, Patent Document 1). The heat recovery system disclosed in Patent Document 1 includes a heat storage tank (system tank) that stores a heat medium that recovers the exhaust heat by heat exchange with the exhaust heat.

Japanese Utility Model Application Publication No. 6-30401

However, when a heat recovery system is started up, it is difficult to supply the specified amount of heat to the facility where it is being used because the temperature of the heat transfer medium is low. Therefore, when a heat recovery system is started up, it is necessary to quickly raise the temperature of the heat transfer medium to the specified temperature.

However, in a heat recovery system equipped with a heat storage tank, such as that disclosed in Patent Document 1, it takes time to raise the temperature of the heat medium in the heat storage tank to a predetermined temperature.

Taking the above facts into consideration, the present invention aims to quickly raise the temperature of the heat medium in the heat storage tank to a predetermined temperature in a heat recovery system.

The heat recovery system according to the first aspect includes a heat source side heat exchanger that exchanges heat generated in a heat source with a heat medium, a utilization side heat exchanger to which the heat medium is supplied from the heat source side heat exchanger, a heat storage tank that stores the heat medium supplied from the heat source side heat exchanger to the utilization side heat exchanger, and a switching means that switches between an operation mode in which the heat medium is circulated among the heat source side heat exchanger, the heat storage tank, and the utilization side heat exchanger, and a start-up mode in which the heat medium is circulated between the heat source side heat exchanger and the heat storage tank, bypassing the utilization side heat exchanger.

According to the heat recovery system of the first aspect , the heat source side heat exchanger exchanges heat generated in the heat source with the heat medium. The heat medium is supplied from the heat source side heat exchanger. The heat medium supplied from the heat source side heat exchanger to the utilization side heat exchanger is stored in the heat storage tank. In the heat storage tank, the heat medium supplied from the heat source side heat exchanger exchanges heat with the heat medium in the heat storage tank, thereby mitigating the amount of temperature change of the heat medium.

The switching means also switches between an operating mode and a start-up mode. In the operating mode, a heat medium is circulated between the heat source side heat exchanger, the heat storage tank, and the utilization side heat exchanger. This allows the heat recovered by the heat source side heat exchanger to be used as a heat source for the utilization side heat exchanger.

On the other hand, when the temperature of the heat medium is low, for example, when the heat recovery system is started up, the switching means switches to the start-up mode. In the start-up mode, the heat medium is circulated between the heat source side heat exchanger and the heat storage tank, bypassing the use side heat exchanger. This allows the temperature of the heat medium in the heat storage tank to be raised to a predetermined temperature more quickly, since the heat medium bypasses the use side heat exchanger.

A heat recovery system according to a second aspect is the heat recovery system according to the first aspect, further comprising : a circulation piping that circulates the heat medium between the heat source side heat exchanger, the heat storage tank, and the use side heat exchanger; a first bypass piping that bypasses the use side heat exchanger and connects the downstream side of the heat storage tank and the downstream side of the use side heat exchanger in the circulation piping; and a second bypass piping that bypasses the use side heat exchanger and connects the downstream side of the heat storage tank and the downstream side of the use side heat exchanger in the circulation piping, on the use side heat exchanger side of the first bypass piping, and wherein the switching means, in the start-up mode, bypasses the use side heat exchanger with the first bypass piping, and then bypasses the use side heat exchanger with the second bypass piping.

The heat recovery system according to the second aspect includes a circulation pipe, a first bypass pipe, and a second bypass pipe. The circulation pipe circulates a heat medium among the heat source side heat exchanger, the heat storage tank, and the utilization side heat exchanger.

The first bypass pipe bypasses the utilization side heat exchanger and connects the downstream side of the heat storage tank to the downstream side of the utilization side heat exchanger in the circulation pipe. The second bypass pipe bypasses the utilization side heat exchanger and connects the downstream side of the heat storage tank to the downstream side of the utilization side heat exchanger in the circulation pipe on the utilization side heat exchanger side of the first bypass pipe.

Here, in the start-up mode, the switching means bypasses the utilization side heat exchanger through the first bypass piping, and then bypasses the utilization side heat exchanger through the second bypass piping.

In this way, the first bypass piping and the second bypass piping can be used to gradually lengthen the circulation path of the heat transfer medium, allowing the temperature of the heat transfer medium to be efficiently increased.

The heat recovery system of the third aspect , in the heat recovery system of the first or second aspect , comprises a first temperature detection unit that detects the temperature of the heat medium in the heat storage tank, a second temperature detection unit that detects the temperature of the heat medium supplied from the heat storage tank to the use side heat exchanger, and a control unit that controls the switching means so that the start-up mode is selected when the temperature of the heat medium detected by the first temperature detection unit is below a reference value, and the operation mode is selected when the temperature of the heat medium detected by the second temperature detection unit is equal to or higher than a reference value.

In the heat recovery system according to the third aspect , the first temperature detector detects the temperature of the heat medium in the heat storage tank. The second temperature detector detects the temperature of the heat medium supplied from the heat storage tank to the utilization-side heat exchanger. The controller controls the switching means based on the temperatures of the heat medium detected by the first temperature detector and the second temperature detector.

Specifically, when the temperature of the heat medium detected by the first temperature detection unit is below a reference value, the control unit controls the switching means to switch to start-up mode, thereby enabling the temperature of the heat medium in the heat storage tank to be raised quickly.

In addition, when the temperature of the heat medium detected by the second temperature detection unit is equal to or higher than a reference value, the control unit controls the switching means to switch to the operating mode. This allows the heat medium whose temperature is equal to or higher than the reference value to be supplied to the user-side heat exchanger.

As described above, according to the present invention, in a heat recovery system, the temperature of the heat medium in the heat storage tank can be raised to a predetermined temperature quickly.

1 is a circuit diagram showing a heat recovery system according to a first embodiment. FIG. 2 is a hardware configuration diagram of a control device according to the first embodiment. 5 is a flowchart illustrating an example of a start-up control process according to the first embodiment. FIG. 5 is a circuit diagram showing a heat recovery system according to a second embodiment. FIG. 5 is an explanatory diagram showing the relationship between the operation mode of the heat recovery system shown in FIG. 4 and the temperature of the heat medium. 6 is an explanatory diagram corresponding to FIG. 5 and illustrating a modified example of a method for controlling the heating heat exchanger shown in FIG. 4.

First Embodiment
First, the first embodiment will be described.

(Heat recovery system)
1 shows a heat recovery system 130 according to a first embodiment. As an example, the heat recovery system 130 is an exhaust heat recovery system (exhaust heat reuse system) that heats low-temperature exhaust heat (low-temperature waste heat) recovered from utilization equipment 10, such as production equipment in the manufacturing industry, with a heat pump 50 and supplies the heat to the utilization equipment 10. The utilization equipment 10 is an example of a heat source.

The heat recovery system 20 includes a heat source side heat exchanger 40, a plurality of heat pumps 50, an auxiliary heat source 60, a heat storage tank 70, a stored heat medium temperature sensor 72, a circulating heat medium temperature sensor 38, a first start-up bypass pipe BP1, a second start-up bypass pipe BP2, switching means (valve VH, first start-up valve V1, second start-up valve V2), an exhaust heat supply status detector 110, and a control device 100 (see FIG. 2).

(Heat source side heat exchanger)
The heat source side heat exchanger 40 is an exhaust heat recovery device that recovers exhaust heat generated in the utilization equipment 10. The heat source side heat exchanger 40 is connected to the utilization equipment 10 via a heat exhaust pipe 12. Exhaust heat such as exhaust gas and exhaust hot water generated in the utilization equipment 10 is supplied to the heat source side heat exchanger 40 via the heat exhaust pipe 12.

The heat source side heat exchanger 40 is connected to a plurality of heat pumps 50 (described later) via a circulation pipe 30. The circulation pipe 30 is formed in an overall ring shape. The circulation pipe 30 has a feed pipe section 30S that supplies heat medium from the heat source side heat exchanger 40 to the plurality of heat pumps 50, and a return pipe section 30R that returns heat medium from the plurality of heat pumps to the heat source side heat exchanger 40. A circulation pump 32 is provided in this circulation pipe 30.

The circulation pump 32 is provided downstream of the heat source heat exchanger 40 in the circulation piping 30 and upstream of the heat pump 50. When the circulation pump 32 is operated, the heat medium flowing in the circulation piping 30 is circulated between the heat source heat exchanger 40 and the heat pump 50. The heat medium is, for example, water or oil.

The heat source side heat exchanger 40 is provided in the bypass pipe section 30B that bypasses the main pipe section 30A of the circulation pipe 30. A pair of valves 42 are provided in the main pipe section 30A and the bypass pipe section 30B of the circulation pipe 30.

The pair of valves 42 are configured to be able to open and close the main pipe section 30A and the bypass pipe section 30B of the circulation pipe 30. By closing the main pipe section 30A and opening the bypass pipe section 30B with the pair of valves 42, the heat medium circulates through the circulation pipe 30 via the heat source side heat exchanger 40.

On the other hand, by opening the main pipe section 30A of the circulation pipe 30 and closing the bypass pipe section 30B using a pair of valves 42, the heat medium circulates through the circulation pipe 30 without passing through the heat source side heat exchanger 40.

The heat source side heat exchanger 40 heats the heat medium by exchanging heat between the exhaust heat supplied from the utilization equipment 10 via the exhaust heat piping 12 and the heat medium flowing through the bypass pipe section 30B of the circulation piping 30. The exhaust heat that passes through the heat source side heat exchanger 40 is treated, for example, as wastewater or exhaust air.

(heat pump)
The multiple heat pumps 50 are heat suppliers that pump heat from a heat medium supplied from the heat source side heat exchanger 40 through the circulation piping 30, thereby generating hot water (high-temperature water) to be supplied to the utilization equipment 10 and the heating heat exchanger 80 described later.

The heat pumps 50 are provided in a number of branch pipe sections 30C that branch in parallel from the circulation pipe 30 and then join together. A valve VH is provided upstream of the heat pump 50 in each branch pipe section 30C. Each valve VH is configured to be able to open and close each branch pipe section 30C.

By opening the branch pipe section 30C with each valve VH, the heat medium is supplied from the circulation pipe 30 to the heat pump 50. On the other hand, by closing the branch pipe section 30C with each valve VH, the supply of the heat medium from the circulation pipe 30 to the heat pump 50 is stopped.

Each heat pump 50 has a low-temperature side heat exchanger (heat absorption side heat exchanger) (not shown), a compressor, a high-temperature side heat exchanger (heat release side heat exchanger), an expander, and circulation piping that circulates the heat medium between the low-temperature side heat exchanger, the compressor, the high-temperature side heat exchanger, and the expander. The low-temperature side heat exchanger is an example of a utilization side heat exchanger.

The low-temperature heat exchanger heats the heat medium by exchanging heat between the heat medium flowing through the circulation piping 30 (branch pipe section 30C) of the heat recovery system 20 and the heat medium flowing through the circulation piping of the heat pump 50. The compressor compresses the heat medium supplied from the low-temperature heat exchanger, increasing the temperature of the heat medium.

The high-temperature side heat exchanger heats the hot water by exchanging heat between the heat medium supplied from the compressor and the hot water supplied from the return pipe 54 described below. The expander expands the heat medium supplied from the high-temperature side heat exchanger, lowering the temperature of the heat medium. The lowered temperature of the heat medium is supplied to the low-temperature side heat exchanger, where it is reheated.

In each heat pump 50, the above cycle is repeated to generate hot water (high-temperature water) in the high-temperature heat exchanger. A hot-water supply header 22 is connected to this high-temperature heat exchanger via a feed pipe 52. A hot-water return header 28 is also connected to the high-temperature heat exchanger via a return pipe 54.

A pump 56 is provided in the return pipe 54. When this pump 56 is operated, hot water is supplied from the hot water return header 28 to the high temperature side heat exchanger of the heat pump 50. In addition, hot water generated in the high temperature side heat exchanger is supplied to the hot water supply header 22 via the delivery pipe 52.

The hot water supply header 22 is connected to the utilization equipment 10 via a feed pipe 24. A pump 25 is provided on the feed pipe 24. When the pump 25 is operated, hot water is supplied from the hot water supply header 22 to the utilization equipment 10, and is used by the utilization equipment 10. At this time, the exhaust heat generated by the utilization equipment 10 is supplied to the heat source side heat exchanger 40 via the exhaust heat pipe 12.

The hot water return header 28 is connected to the utilization equipment 10 via a return pipe 26. The hot water used in the utilization equipment 10 is discharged to the hot water return header 28 via the return pipe 26. The hot water return header 28 is connected to a plurality of heat pumps 50 via the return pipes 54 described above.

The number of heat pumps 50 is not limited to multiple, but at least one is sufficient. Furthermore, the heat pump 50 is not limited to a hot water heat pump that generates hot water, and may be, for example, a heat pump (industrial heat pump) such as a steam heat pump that generates steam or a hot air heat pump that generates hot air.

(auxiliary heat source)
The auxiliary heat source 60 is, for example, a heater such as a boiler that uses primary energy generated by burning fossil fuels, etc. as a heat source. The auxiliary heat source 60 generates hot water to be supplied to the utilization facility 10 and the heating heat exchanger 80.

The auxiliary heat source 60 is connected to the hot water supply header 22 via a feed pipe 62. The auxiliary heat source 60 is also connected to the hot water return header 28 via a return pipe 64. A pump 66 is provided on the return pipe 64. When the pump 66 is operated, hot water is supplied from the hot water return header 28 to the auxiliary heat source 60, and hot water generated by the auxiliary heat source 60 is supplied to the hot water supply header 22 via the feed pipe 62.

The auxiliary heat source 60 is not limited to a heater such as a boiler that uses primary energy as a heat source, but may also be, for example, a heat pump.

(Heat storage tank)
A heat storage tank 70 is provided downstream of the heat source side heat exchanger 40 and upstream of the heat pump 50 in the circulation piping 30. The heat storage tank 70 is an insulation tank that stores the heat medium supplied from the heat source side heat exchanger 40 to the heat pump 50 while keeping it warm. By supplying the heat medium from the heat source side heat exchanger 40 to the heat pump 50 through this heat storage tank 70, the amount of temperature change of the heat medium is mitigated.

(Temperature sensor for stored heat medium)
The heat storage tank 70 is provided with a stored heat medium temperature sensor 72. The stored heat medium temperature sensor 72 detects the temperature of the heat medium stored in the heat storage tank 70 and outputs the temperature to a control device 100 described later. The stored heat medium temperature sensor 72 is an example of a first temperature detection unit.

(Circulating heat transfer medium temperature sensor)
A circulating heat medium temperature sensor 38 is provided upstream of the heat pumps 50 in the circulation piping 30 and downstream of the heat storage tank 70. The circulating heat medium temperature sensor 38 detects the temperature of the heat medium flowing through the circulation piping 30 and outputs the detected temperature information to the control device 100 described later. The circulating heat medium temperature sensor 38 is an example of a second temperature detection unit.

(First startup bypass piping)
The circulation piping 30 is provided with a first start-up bypass piping BP1 that bypasses the multiple heat pumps 50 and supplies the heat medium downstream of the heat storage tank 70 to the heat source side heat exchanger 40. The first start-up bypass piping is an example of the first bypass piping.

The first startup bypass pipe BP1 branches off from the circulation pipe 30 downstream of the heat storage tank 70 and upstream of the multiple heat pumps 50, and is connected to the circulation pipe 30 downstream of the multiple heat pumps 50 and upstream of the heat source side heat exchanger 40.

More specifically, one end of the first start-up bypass piping BP1 is connected downstream of the heat storage tank 70 and the circulating heat medium temperature sensor 38 in the circulation piping 30 and upstream of the heat pumps 50. The other end of the first start-up bypass piping BP1 is connected downstream of the heat pumps 50 in the circulation piping 30 and upstream of the heat source side heat exchanger 40.

The first start-up bypass pipe BP1 is provided with a first start-up valve V1. The first start-up valve V1 is configured to be able to open and close the first start-up bypass pipe BP1.

(Second startup bypass piping)
The circulation piping 30 is provided with a second start-up bypass piping BP2 on the heat pump 50 side of the first start-up bypass piping BP1, which bypasses the heat pumps 50 and supplies the heat medium downstream of the heat storage tank 70 to the heat source side heat exchanger 40. The second start-up bypass piping is an example of the second bypass piping.

The second startup bypass piping BP2 is an extension piping that extends the circulation piping 30 so as to bypass the multiple heat pumps 50. More specifically, the second startup bypass piping BP2 connects an end of the feed pipe section 30S of the circulation piping 30 that sends the heat medium to the multiple heat pumps 50, and an end of the return pipe section 30R that returns the heat medium discharged from the multiple heat pumps 50 to the heat source side heat exchanger 40.

The second start-up bypass pipe BP2 is provided with a second start-up valve V2. The second start-up valve V2 is configured to be able to open and close the second start-up bypass pipe BP2.

(Switching Means)
The switching means switches the operation mode of the heat recovery system 130 between the startup mode and the operating mode by opening and closing the branch pipes 30C of the circulation pipe 30, the first startup bypass pipe BP1, and the second startup bypass pipe BP2 to switch the flow path through which the heat medium flows. This switching means has the valves VH for each heat pump 50 described above, the first startup valve V1, and the second startup valve V2.

(Exhaust heat supply status detector)
The exhaust heat supply status detector 110 detects whether or not exhaust heat is being supplied from the utilization equipment 10 to the heat source side heat exchanger 40, and outputs the detected exhaust heat supply information to the control device 100. The exhaust heat supply status detector 110 detects the exhaust heat supply information, for example, by detecting the operating status of a drainage pump or an exhaust fan that sends exhaust heat from the utilization equipment 10 to the heat source side heat exchanger 40.

(Control device)
2, the control device 100 controls the overall operation of the heat recovery system 130 (see FIG. 1). The control device 100 is configured, for example, by a programmable logic controller (PLC).

The control device 100 includes a CPU (Central Processing Unit) 102, a memory 104 as a temporary storage area, and a non-volatile storage unit 106. The control device 100 also includes an input/output device 108. The CPU 102, memory 104, storage unit 106, and input/output device 108 are connected to each other via a bus 109. The CPU 102 is an example of a control unit.

The storage unit 106 is realized by, for example, a hard disk drive (HDD), a solid state drive (SSD), a flash memory, etc. A startup control program that controls the operation of the heat recovery system 130 is stored in advance in the storage unit 106 as a recording medium.

The CPU 102 reads the start-up control program from the storage unit 106, loads it into the memory 104, and executes each step of the start-up control program in sequence. The storage unit 106 also stores a reference value T for the heat medium in advance.

The CPU 102 that executes the heat medium temperature control program is hardware. The functions realized by the heat medium temperature control program can also be realized by, for example, a semiconductor integrated circuit, more specifically, an ASIC (Application Specific Integrated Circuit), etc.

The control device 100 is electrically connected to the pump 25, the circulation pump 32, the circulating heat medium temperature sensor 38, a pair of valves 42 for the heat source side heat exchanger 40, the heat pump 50, the valves VH for each heat pump 50, the pumps 56, 66, and the auxiliary heat source 60. In addition, the control device 100 is electrically connected to the first start-up valve V1, the second start-up valve V2, the stored heat medium temperature sensor 72, and the exhaust heat supply status detector 110.

(Control method of heat recovery system)
Next, an example of a method for controlling the heat recovery system 130 will be described while explaining the operation of the control device 100.

When the heat recovery system 130 is started up, the temperature of the heat medium is low, making it difficult to supply the specified amount of heat to the utilization facility 10. Therefore, when the heat recovery system 130 is started up, it is necessary to quickly raise the temperature of the heat medium to the specified temperature. However, it takes time to raise the temperature of the heat medium in the heat storage tank 70 to the specified temperature.

To cope with this, the heat recovery system 130 of this embodiment has a start-up mode and an operation mode. The CPU 102 of the control device 100 controls the switching means (valve VH, first start-up valve V1, second start-up valve V2) based on the temperatures _t1 and _t2 of the heat medium detected by the stored heat medium temperature sensor 72 and the circulating heat medium temperature sensor 38, to switch the operation mode of the heat recovery system 130.

Specifically, when the heat recovery system 130 is started up, the control device 100 executes the start-up control process shown in FIG. 3. The start-up control process is an example of a start-up control method. When the heat recovery system 130 is stopped, the first start-up valve V1, the second start-up valve V2, and the valves VH for each heat pump 50 are closed. The circulation pump 32 is stopped.

From this state, the CPU 102 first determines in step S10 whether or not exhaust heat is being supplied from the utilization equipment 10 to the heat source side heat exchanger 40 based on the exhaust heat supply status detected by the exhaust heat supply status detector 110. Then, if it is determined that exhaust heat is not being supplied from the utilization equipment 10 to the heat source side heat exchanger 40, the CPU 102 executes step S10 again after a predetermined time has elapsed.

On the other hand, if it is determined that exhaust heat is being supplied from the utilization equipment 10 to the heat source side heat exchanger 40, the CPU 102 proceeds to step S12.

In step S12, the CPU 102 compares the temperature _t1 of the heat medium in the heat storage tank 70 detected by the stored heat medium temperature sensor 72 with a reference value T. Then, when the temperature _t1 is equal to or higher than the reference value T ( _t1 ≧T), the CPU 102 controls the switching means to operate the heat recovery system 130 in the operation mode.

That is, in step S14, the CPU 102 operates the valve VH for each heat pump 50 and opens each branch pipe section 30C of the circulation pipe 30. Next, in step S16, the CPU 102 operates the circulation pump 32. Next, in step S30, the CPU 102 operates the heat pump 50.

As a result, as shown by arrow a in FIG. 1, the heat medium is circulated through the circulation piping 30 between the heat source side heat exchanger 40, the heat storage tank 70, and the multiple heat pumps 50. As a result, hot water is supplied from each heat pump 50 to the utilization equipment 10 through the feed piping 52, the hot water feed header 22, and the feed piping 24.

On the other hand, in step S12, when the temperature _t1 is less than the reference value T ( _t1 < T), the CPU 102 controls the switching means to operate the heat recovery system 130 in the start-up mode. That is, in step S18, the CPU 102 operates the first start-up valve V1 and opens the first start-up bypass pipe BP1. Next, in step S20, the CPU 102 operates the circulation pump 32.

As a result, as shown by the arrow f1 in FIG. 1, the heat medium downstream of the heat storage tank 70 in the circulation piping 30 is supplied to the heat source side heat exchanger 40 via the first startup bypass piping BP1. In other words, the heat medium is circulated between the heat source side heat exchanger 40 and the heat storage tank 70, bypassing the multiple heat pumps 50. This allows the temperature of the heat medium in the heat storage tank 70 to rise quickly.

Next, in step S22, the CPU 102 waits for a predetermined time. This predetermined time is set, for example, based on the flow rate of the heat medium, to a time during which the heat medium stored in advance in the heat storage tank 70 can be replaced with the heat medium heated in the heat source side heat exchanger 40.

Next, in step S24, the CPU 102 activates the first start-up valve V1 and the second start-up valve V2, closes the first start-up bypass pipe BP1, and opens the second start-up bypass pipe BP2.

As a result, as shown by the arrow f2 in FIG. 1, the heat medium that has accumulated in the feed pipe section 30S and the return pipe section 30R of the circulation pipe 30 on the side of the multiple heat pumps 50 from the first start-up bypass pipe BP1 flows and is supplied to the heat source side heat exchanger 40.

Next, in step S26, the CPU 102 compares the temperature _t2 of the heat medium in the circulation piping 30 detected by the circulating heat medium temperature sensor 38 with a reference value T. Then, if the temperature _t2 is less than the reference value T ( _t2 < T), the CPU 102 executes step S26 again.

On the other hand, in step S26, if the temperature _t2 is equal to or higher than the reference value T ( _t2 ≥ T), the CPU 102 controls the switching means to switch the operation mode of the heat recovery system 130 from the start-up mode to the operating mode.

That is, in step S28, the CPU 102 activates the second start-up valve V2 and closes the second start-up bypass pipe BP2. The CPU 102 also activates the valves VH for each heat pump 50 and opens each branch pipe section 30C of the circulation pipe 30.

As a result, the heat medium is circulated between the heat source side heat exchanger 40, the heat storage tank 70, and the multiple heat pumps 50 via the circulation piping 30. As a result, hot water is supplied from each heat pump 50 to the utilization equipment 10 via the feed piping 52, the hot water feed header 22, and the feed piping 24.

(Action and Effects)
Next, the operation and effects of the first embodiment will be described.

As described above, the switching means (valve VH, first start-up valve V1, second start-up valve V2) can switch the operation mode of the heat recovery system 130 between the operating mode and the start-up mode. In the operating mode, the heat medium is circulated between the heat source side heat exchanger 40, the heat storage tank 70, and the multiple heat pumps 50. This allows the heat recovered by the heat source side heat exchanger 40 to be used as a heat source for the multiple heat pumps 50.

On the other hand, when the temperature of the heat medium is low, for example, when the heat recovery system 130 is started up, the switching means sets the operation mode of the heat recovery system 130 to the start-up mode. In the start-up mode, the heat medium is circulated between the heat source side heat exchanger 40 and the heat storage tank 70, bypassing the multiple heat pumps 50. As a result, the temperature of the heat medium in the heat storage tank 70 can be raised to a predetermined temperature more quickly because the heat medium bypasses the multiple heat pumps 50. In addition, the temperature of the heat medium in the circulation piping 30 that circulates the heat medium between the heat source side heat exchanger 40 and the heat storage tank 70 can also be raised to a predetermined temperature more quickly.

The circulation piping 30 is also provided with a first start-up bypass piping BP1 and a second start-up bypass piping BP2. The circulation piping 30 circulates the heat medium between the heat source side heat exchanger 40, the heat storage tank 70, and the multiple heat pumps 50.

The first start-up bypass piping BP1 bypasses the multiple heat pumps 50 and connects the downstream side of the heat storage tank 70 in the circulation piping 30 to the downstream side of the multiple heat pumps 50. The second start-up bypass piping BP2 bypasses the multiple heat pumps 50 and connects the downstream side of the heat storage tank 70 in the circulation piping 30 to the downstream side of the multiple heat pumps 50 on the multiple heat pumps 50 side of the first start-up bypass piping BP1.

Here, in the start-up mode, the switching means bypasses the multiple heat pumps 50 through the first start-up bypass piping BP1, and then bypasses the multiple heat pumps 50 through the second start-up bypass piping BP2.

In this way, the first start-up bypass pipe BP1 and the second start-up bypass pipe BP2 can be used to gradually lengthen the circulation path of the heat transfer medium, thereby efficiently increasing the temperature of the heat transfer medium.

Furthermore, the stored heat medium temperature sensor 72 detects the temperature of the heat medium in the heat storage tank 70. Furthermore, the circulating heat medium temperature sensor 38 detects the temperature of the heat medium supplied from the heat storage tank 70 to the multiple heat pumps 50. Then, the CPU 102 controls the switching means based on the temperatures _t1 , t2 of the heat medium detected by the stored heat medium temperature sensor ₇₂ and the circulating heat medium temperature sensor 38.

Specifically, when the temperature _t1 of the heat medium detected by the stored heat medium temperature sensor 72 is less than the reference value T, the CPU 102 controls the switching means to set the operation mode of the heat recovery system 130 to the start-up mode. This causes the temperature of the heat medium in the heat storage tank 70 to rise.

Furthermore, when the temperature _t2 of the heat medium detected by the circulating heat medium temperature sensor 38 is equal to or higher than the reference value T, the CPU 102 controls the switching means to switch the operation mode of the heat recovery system 130 from the start-up mode to the operating mode. This makes it possible to supply the heat medium having a temperature equal to or higher than the reference value T to the multiple heat pumps 50.

In this way, by controlling the switching means with the CPU 102 of the control device 100, the temperature of the heat medium in the heat storage tank 70 can be efficiently increased when the heat recovery system 130 is started up.

(Modification of the first embodiment)
Next, a modification of the first embodiment will be described.

In the first embodiment described above, in the start-up mode, the heat medium flowing through the circulation pipe 30 is heated by the heat source side heat exchanger 40. However, for example, in the start-up mode, the heat medium flowing through the circulation pipe 30 may be heated by at least one of the heat source side heat exchanger 40 and the heating heat exchanger 80 (see FIG. 4) described later.

In this case, for example, in step S18 of the flowchart shown in FIG. 3, the CPU 102 operates a pair of valves 82 for the heating heat exchanger 80, closes the main pipe section 30A of the circulation piping 30, and opens the heating bypass pipe section 30D.

In step S18, the CPU 102 also operates the pump 88 to supply hot water from the hot water supply header 22 to the heating heat exchanger 80 via the feed pipe 84, as shown by arrow b (see FIG. 1). This causes heat exchange between the hot water and the heat medium in the heating heat exchanger 80, heating the heat medium. As a result, the temperature of the heat medium in the heat storage tank 70 can be raised quickly.

In the start-up mode, the heat pump 50 is not operating, so the heat source for the heating heat exchanger 80 is the auxiliary heat source 60.

In the first embodiment, the CPU 102 controlled the switching means based on the temperature of the heat medium detected by the circulating heat medium temperature sensor 38 and the stored heat medium temperature sensor 72. However, the CPU 102 may calculate the temperature change per unit time (e.g., 1 minute) of the heat medium relative to a reference value based on the temperatures of the heat medium detected by each of the circulating heat medium temperature sensor 38 and the stored heat medium temperature sensor 72, and control the switching means based on these temperature change amounts. The CPU 102 may also control the switching means based on the temperature of the heat medium detected by at least one of the circulating heat medium temperature sensor 38 and the stored heat medium temperature sensor 72, for example.

The switching means in the first embodiment is configured to include the valve VH, the first start-up valve V1, and the second start-up valve V2. However, the configuration of the switching means may be modified as appropriate. For example, a three-way valve may be used instead of the valve VH. Similarly, a three-way valve may be used instead of the first start-up valve V1 and the second start-up valve V2.

In the first embodiment, the first start-up bypass pipe BP1 and the second start-up bypass pipe BP2 are connected to the circulation pipe 30. However, the second start-up bypass pipe BP2 can be omitted as appropriate.

Second Embodiment
Next, a second embodiment will be described. In the second embodiment, the same reference numerals will be used to designate the same components as those in the first embodiment, and the description thereof will be omitted as appropriate.

Figure 4 shows a heat recovery system 20 according to the second embodiment. The heat recovery system 20 includes a heating heat exchanger 80, a temperature-reducing bypass pipe 34, a switching means (a pair of valves 82 and a three-way valve 36), and a control device 100.

(heat exchanger for heating)
A heating heat exchanger 80 is provided downstream of the heat storage tank 70 in the circulation piping 30 and upstream of the heat pump 50. The heating heat exchanger 80 is a heater that heats the heat medium flowing through the circulation piping 30. The heating heat exchanger 80 is an example of a heater. The heating heat exchanger 80 is provided upstream of the circulation pump 32 and the circulating heat medium temperature sensor 38.

The heating heat exchanger 80 is provided in the heating bypass pipe section 30D, which bypasses the main pipe section 30A of the circulation pipe 30. A pair of valves 82 are provided in the main pipe section 30A of the circulation pipe 30 and the heating bypass pipe section 30D.

The pair of valves 82 are configured to open and close the main pipe section 30A of the circulation pipe 30 and the heating bypass pipe section 30D, respectively. By opening the heating bypass pipe section 30D and closing the main pipe section 30A of the circulation pipe 30 with the pair of valves 82, the heat medium circulates through the circulation pipe 30 via the heating heat exchanger 80.

On the other hand, by closing the heating bypass pipe section 30D and opening the main pipe section 30A of the circulation pipe 30 using a pair of valves 82, the heat medium circulates through the circulation pipe 30 without passing through the heating heat exchanger 80.

The hot water supply header 22 is connected to the heating heat exchanger 80 via a feed pipe 84. The hot water return header 28 is also connected to the heating heat exchanger 80 via a return pipe 86. A pump 88 is provided on the feed pipe 84. When the pump 88 is operated, hot water is supplied from the hot water supply header 22 to the heating heat exchanger 80, and hot water is discharged from the heating heat exchanger 80 to the hot water return header 28 via the return pipe 86.

The heating heat exchanger 80 heats the heat medium by exchanging heat between the hot water supplied from the hot water supply header 22 through the feed pipe 84 and the heat medium flowing through the heating bypass pipe section 30D. In other words, the heating heat exchanger 80 heats the heat medium flowing through the circulation pipe 30 using at least one of the heat pump 50 and the auxiliary heat source 60 as a heat source.

The feed pipe 84 is also provided with a flow rate control valve 89. By increasing or decreasing the opening of the feed pipe 84 with this flow rate control valve 89, the flow rate of the hot water supplied from the feed pipe 84 to the heating heat exchanger 80 is adjusted.

(Bypass piping for cooling)
The circulation piping 30 is provided with a temperature-reducing bypass piping 34 that bypasses the heat source-side heat exchanger 40 and the heat storage tank 70 and supplies the heat medium downstream of the heat pump 50 to the heat pump 50. The temperature-reducing bypass piping 34 branches off from a three-way valve 36 provided in the circulation piping 30 downstream of the heat pumps 50 and upstream of the heat source-side heat exchanger 40, and is connected to the circulation piping 30 upstream of the heat pumps 50 and downstream of the heat storage tank 70.

More specifically, one end of the temperature-reducing bypass piping 34 is connected to a three-way valve 36 provided downstream of the heat pumps 50 in the circulation piping 30 and upstream of the heat source heat exchanger 40. The other end of the temperature-reducing bypass piping 34 is connected upstream of the heat pumps 50, the circulation pump 32, the circulating heat medium temperature sensor 38, and the heating heat exchanger 80 in the circulation piping 30 and downstream of the heat storage tank 70.

The temperature-reducing bypass pipe 34 and the circulation pipe 30 form a temperature-reducing circulation flow path that circulates the heat medium to the multiple heat pumps 50, bypassing the heat source side heat exchanger 40 and the heat storage tank 70. The circulation pump 32 and the circulating heat medium temperature sensor 38 are provided in the temperature-reducing circulation flow path. The temperature-reducing bypass pipe 34 is connected to the circulation pipe 30 on the heat source side heat exchanger 40 side relative to the first start-up bypass pipe BP1 and the second start-up bypass pipe BP2.

The three-way valve 36 is configured to be able to open and close the circulation pipe 30 and the temperature-reducing bypass pipe 34. By opening the circulation pipe 30 and closing the temperature-reducing bypass pipe 34 with the three-way valve 36, the heat medium is supplied from the multiple heat pumps 50 to the heat source side heat exchanger 40 via the circulation pipe 30.

On the other hand, by closing the circulation pipe 30 and opening the temperature-reducing bypass pipe 34 using the three-way valve 36, the heat medium downstream of the multiple heat pumps 50 is supplied to the upstream side of the multiple heat pumps 50 via the temperature-reducing bypass pipe 34.

The three-way valve 36 is configured to be able to open and close the circulation pipe 30 and the temperature-reducing bypass pipe 34 independently. By increasing or decreasing the opening of the circulation pipe 30 and the temperature-reducing bypass pipe 34 using this three-way valve 36, the flow rate of the heat medium flowing from the three-way valve 36 to the heat source side heat exchanger 40 and the flow rate of the heat medium flowing to the temperature-reducing bypass pipe 34 can be adjusted.

(Switching Means)
The switching means switches the operation mode of the heat recovery system 20 among the normal mode, the temperature increase mode, and the temperature decrease mode by opening and closing the circulation piping 30, the heating bypass pipe section 30D, and the temperature decrease bypass piping 34 to switch the flow path through which the heat medium flows. This switching means has a pair of valves 82 for the heating heat exchanger 80 and the three-way valve 36 for the temperature decrease bypass piping 34 described above.

(Control device)
The control device 100 is electrically connected to the three-way valve 36 , a pair of valves 82 for the heating heat exchanger 80 , a pump 88 , and a flow rate adjustment valve 89 .

2, the storage unit 106 prestores a heat medium temperature control program for controlling the operation of the heat recovery system 20. The CPU 102 reads out the heat medium temperature control program from the storage unit 106, loads it into the memory 104, and executes each step of the heat medium temperature control program. The storage unit 106 also prestores a lower limit T _min , a first threshold T ₁ , a second threshold T ₂ , and an upper limit T _max of the heat medium (T _min < T ₁ < T ₂ < T _max ).

(Control method of heat recovery system)
Next, an example of a method for controlling the heat recovery system 20 will be described while explaining the operation of the control device 100.

As described above, the heat recovery system 20 according to this embodiment is an exhaust heat recovery system (exhaust heat reuse system) that heats low-temperature exhaust heat recovered from the utilization equipment 10 using multiple heat pumps 50 and supplies the heat to the utilization equipment 10.

The amount of exhaust heat generated by the utilization equipment 10 varies depending on the operating conditions, etc. Therefore, the amount of exhaust heat supplied from the utilization equipment 10 to the heat source side heat exchanger 40 via the exhaust heat piping 12 varies depending on the operating conditions, etc. of the utilization equipment 10. This causes the amount of exhaust heat recovered by the heat source side heat exchanger 40 to vary, which may cause the temperature of the heat medium flowing through the circulation piping 30 to fluctuate.

When the temperature of the heat medium fluctuates, the amount of heat pumped by each heat pump 50 also fluctuates, and it may not be possible to supply hot water at a specified temperature to the utilization equipment 10. Furthermore, when the temperature of the heat medium fluctuates suddenly, the expansion valve or compressor of each heat pump 50 may malfunction, causing each heat pump 50 to stop or break down.

As a countermeasure against this, the heat recovery system 20 of this embodiment has three operation modes, a normal mode, a temperature increase mode, and a temperature decrease mode, as shown in Fig. _4. The CPU 102 controls the switching means (the pair of valves 82 and the three-way valve ₃₆ ) so that the normal mode is selected when the temperature of the heat medium detected by the circulating heat medium temperature sensor 38 is equal to or higher than a first threshold value _T1 and equal to or lower than a second threshold value T2, the temperature increase mode is selected when the temperature of the heat medium is lower than the first threshold value _T1 , and the temperature decrease mode is selected when the temperature of the heat medium exceeds the second threshold value T2.

Furthermore, the CPU 102 stops the heat recovery system 20 when the temperature of the heat medium detected by the circulating heat medium temperature sensor 38 is lower than the lower limit value T _min or exceeds the upper limit value T _max .

When the heat recovery system 20 is operating, regardless of the operating mode, a pair of valves 42 are opened and closed so that the heat medium is supplied to the heat source side heat exchanger 40, and valve VH is opened so that the heat medium is supplied to the multiple heat pumps 50. In addition, the first start-up valve V1 and the second start-up valve V2 are closed. Furthermore, each of the pumps 25, 56, 66, the circulation pump 32, and the auxiliary heat source 60 are operated.

On the other hand, when the heat recovery system 20 is stopped, a pair of valves 42 are opened and closed so that the heat medium is not supplied to the heat source side heat exchanger 40, and the valve VH is closed so that the heat medium is not supplied to the multiple heat pumps 50. In addition, each pump 25, 56, 66, the circulation pump 32, and the auxiliary heat source 60 are stopped. Note that the auxiliary heat source 60 may be operated regardless of whether the heat recovery system 20 is operating or stopped.

(Normal mode)
First, the normal mode will be described. The normal mode is an operation mode when, for example, the amount of exhaust heat supplied from the utilization facility 10 (heat source) to the heat source side heat exchanger 40 is stable within a predetermined range. When the temperature of the heat medium detected by the circulating heat medium temperature sensor 38 is equal to or higher than the first threshold value _T1 and equal to or lower than the second threshold value _T2 , the CPU 102 controls the switching means to set the operation mode of the heat recovery system 20 to the normal mode.

Specifically, the CPU 102 operates a pair of valves 82 for the heating heat exchanger 80, opens the main pipe section 30A of the circulation pipe 30, and closes the heating bypass pipe section 30D. The CPU 102 also operates the three-way valve 36, opens the circulation pipe 30, and closes the cooling bypass pipe 34.

As a result, as shown by arrow a in FIG. 4, the heat medium is circulated between the heat source side heat exchanger 40 and the multiple heat pumps 50 via the circulation piping 30. As a result, the heat medium heated by the heat source side heat exchanger 40 is supplied to each of the multiple heat pumps 50. Each heat pump 50 generates hot water by exchanging heat pumped from the heat medium with hot water supplied from the return piping 54.

The hot water generated by each heat pump 50 is supplied to the utilization equipment 10 via the delivery pipe 52, the hot water delivery header 22, and the delivery pipe 24. In addition, the hot water used in the utilization equipment 10 is supplied to each heat pump 50 via the return pipe 26, the hot water return header 28, and the return pipe 54, and is reheated in each heat pump 50.

When the hot water is used in the utilization facility 10, exhaust heat is generated. This exhaust heat is supplied to the heat source side heat exchanger 40 via the exhaust heat piping 12 and is reused as a heat source for heating the heat medium.

When the heat recovery system 20 is in operation, it first goes into normal mode.

(heating mode)
Next, the heating mode will be described. The heating mode is set as an operating mode when the amount of exhaust heat supplied from the utilization equipment 10 (heat source) to the heat source side heat exchanger 40 decreases, and is switched from the normal mode. That is, when the temperature of the heat medium detected by the circulating heat medium temperature sensor 38 is equal to or higher than the lower limit value _Tmin and lower than the first threshold value _T1 , the CPU 102 controls the switching means to switch from the normal mode to the heating mode.

Specifically, the CPU 102 operates a pair of valves 82 for the heating heat exchanger 80, closes the main pipe section 30A of the circulation piping 30, and opens the heating bypass pipe section 30D. As a result, as shown by arrow b, the heat medium is supplied from the circulation piping 30 through the heating bypass pipe section 30D to the heating heat exchanger 80.

The CPU 102 also operates the pump 88 to supply hot water from the hot water supply header 22 to the heating heat exchanger 80 via the feed piping 84. As a result, in the heating heat exchanger 80, heat is exchanged between the heat medium supplied from the heating bypass pipe section 30D and the hot water supplied from the feed piping 84, and the heat medium is heated. As a result, the temperature of the heat medium supplied to the multiple heat pumps 50 via the circulation piping 30 increases.

At this time, as shown in graph G2 in Fig. 5, the CPU 102 controls the aperture of the flow rate control valve ₈₉ and _gradually opens the feed pipe 84 so that the flow rate of hot water supplied from the hot water supply header 22 to the heating heat exchanger 80 increases as the temperature of the heat medium detected by the circulating heat medium temperature sensor 38 approaches the lower limit value Tmin from the first threshold value T1. This makes it possible to efficiently increase the temperature of the heat medium supplied from the heating bypass pipe section 30D in the heating heat exchanger 80.

Graph G1 in FIG. 5 shows the relationship between the amount of heat medium supplied from the circulation piping 30 to the heating heat exchanger 80 via the heating bypass pipe section 30D and the temperature of the heat medium.

Then, when the temperature of the heat medium detected by the circulating heat medium temperature sensor 38 becomes equal to or higher than the first threshold value _T1 and equal to or lower than the second threshold value _T2 , the CPU 102 controls the switching means (the pair of valves 82, the three-way valve 36) to switch from the heating mode to the normal mode.

On the other hand, when the temperature of the heat medium detected by the circulating heat medium temperature sensor 38 falls below the lower limit value T _min , the CPU 102 stops the heat recovery system 20 (see graph G4 in FIG. 5).

(Cooling down mode)
Next, the temperature decreasing mode will be described. The temperature decreasing mode is an operation mode when, for example, the amount of exhaust heat supplied from the utilization equipment 10 (heat source) to the heat source side heat exchanger 40 increases, and is switched from the normal mode. That is, when the temperature of the heat medium detected by the circulating heat medium temperature sensor 38 exceeds the second threshold value _T2 and is equal to or lower than the upper limit value _Tmax , the CPU 102 controls the switching means (three-way valve 36) to switch from the normal mode to the temperature decreasing mode.

Specifically, the CPU 102 operates the three-way valve 36 to close the circulation pipe 30 and open the temperature-reducing bypass pipe 34. As a result, as shown by arrow c in FIG. 4, the heat medium downstream of the multiple heat pumps 50 is supplied to the upstream side of the multiple heat pumps 50 via the temperature-reducing bypass pipe 34. In other words, the heat medium downstream of the multiple heat pumps 50 is supplied to the upstream side of the multiple heat pumps 50, bypassing the heat source-side heat exchanger 40 and the heat storage tank 70.

As a result, the temperature of the heat medium drops by the amount that the heat medium bypasses the heat source side heat exchanger 40. Also, by bypassing the heat storage tank 70, the temperature of the heat medium supplied to the heat pump 50 can be reduced quickly.

At this time, the CPU 102 controls the aperture of the three-way valve 36 so that the flow rate of the heat medium flowing through the temperature-reducing bypass piping 34 increases as the temperature of the heat medium detected by the circulating heat medium temperature sensor 38 approaches the upper limit value _Tmax from the second threshold value _T2 , and gradually closes the circulation piping 30 and gradually opens the temperature-reducing bypass piping 34, as shown in graph G3 in Fig. 5. This makes it possible to efficiently reduce the temperature of the heat medium.

Then, when the temperature of the heat medium detected by the circulating heat medium temperature sensor 38 becomes equal to or higher than the first threshold value _T1 and equal to or lower than the second threshold value _T2 , the CPU 102 controls the switching means (three-way valve 36) to switch from the heating mode to the normal mode.

On the other hand, when the temperature of the heat medium detected by the circulating heat medium temperature sensor 38 exceeds the upper limit value _Tmax , the CPU 102 stops the heat recovery system 20 (see graph G4 in FIG. 5).

(Action and Effects)
Next, the operation and effects of the second embodiment will be described.

As described above, the switching means (the pair of valves 82, the three-way valve 36) switches the operation mode of the heat recovery system 20 between the normal mode, the temperature increase mode, and the temperature decrease mode. In the normal mode, the heat medium is circulated between the heat source side heat exchanger 40 and the heat pump 50. This allows the heat recovered by the heat source side heat exchanger 40 to be used as a heat source for the heat pump 50.

In addition, in the heating mode, the heat medium is circulated between the heat source side heat exchanger 40 and the heat pump 50, and the heating heat exchanger 80 is caused to heat the heat medium. Therefore, for example, when the temperature of the heat medium is low, the temperature of the heat medium can be increased by switching from the normal mode to the heating mode using the switching means.

On the other hand, in the temperature reduction mode, the heat medium downstream of the heat pump 50 is supplied to the heat pump 50, bypassing the heat source side heat exchanger 40. As a result, for example, when the temperature of the heat medium is high, the temperature of the heat medium can be reduced by switching from the normal mode to the temperature reduction mode using the switching means.

In this way, by switching between normal mode, heating mode, and cooling mode using the switching means (the pair of valves 82 and the three-way valve 36), temperature changes in the heat medium are suppressed. As a result, the temperature of the heat medium supplied to the heat pump 50 is stabilized. Therefore, heat can be stably supplied from the heat pump 50 to, for example, the utilization facility 10.

The heat storage tank 70 also stores the heat medium supplied from the heat source side heat exchanger 40. In this heat storage tank 70, the heat medium supplied from the heat source side heat exchanger 40 is heat exchanged with the heat medium in the heat storage tank 70, thereby mitigating the amount of temperature change in the heat medium.

Furthermore, in the temperature reduction mode, the switching means supplies the heat medium downstream of the heat pump 50 to the heat pump 50, bypassing the heat source side heat exchanger 40 and the heat storage tank 70. This allows the temperature of the heat medium to be reduced without being affected by the heat medium stored in the heat storage tank 70. Therefore, the temperature of the heat medium can be reduced efficiently.

In addition, in the temperature increase mode, the heating heat exchanger 80 heats the heat medium using at least one of the multiple heat pumps 50 and the auxiliary heat source 60 as a heat source.

In this way, by using the heat pump 50 as the heat source for the heating heat exchanger 80, energy savings can be achieved. In addition, by using the auxiliary heat source 60 as the heat source for the heating heat exchanger 80, the temperature of the heat medium can be increased in the temperature increase mode even when a sufficient amount of heat is not available from the heat pump 50.

Furthermore, in this embodiment, as described above, the CPU 102 of the control device 100 controls the switching means based on the temperature of the heat medium detected by the circulating heat medium temperature sensor 38. By controlling the switching means by the CPU 102 of the control device 100 in this manner, it is possible to efficiently suppress temperature changes in the heat medium.

(Modification of the second embodiment)
Next, a modification of the second embodiment will be described.

In the second embodiment described above, in the temperature rise mode, the CPU 102 controls the opening degree of the flow control valve 89 so that the flow rate of hot water supplied from the hot water supply header 22 to the heating heat exchanger 80 increases as the temperature of the heat medium detected by the circulating heat medium temperature sensor ₃₈ approaches the lower limit value Tmin from _the first threshold value T1.

However, for example, as shown in a modified graph G1 in FIG. 6 , the CPU 102 may control the apertures of the pair of valves 82 so that the flow rate of the heat medium supplied from the circulation pipe 30 to the heating heat exchanger 80 increases as the temperature of the heat medium detected by the circulating heat medium temperature sensor ₃₈ approaches the lower limit _value Tmin from the first threshold value T1.

Furthermore, the CPU 102 can also fully open the flow rate control valve 89 when the temperature of the heat medium detected by the circulating heat medium temperature sensor 38 becomes less than the first threshold value _T1 . Similarly, the CPU 102 can also control the three-way valve 36 to close the circulation pipe 30 and fully open the temperature-lowering bypass pipe 34 when the temperature of the heat medium detected by the circulating heat medium temperature sensor 38 exceeds the first threshold value _T2 .

In the second embodiment, the CPU 102 controlled the switching means based on the temperature of the heat medium detected by the circulating heat medium temperature sensor 38. However, the CPU 102 may calculate the amount of temperature change per unit time (e.g., 1 minute) of the heat medium relative to a reference value based on the temperature of the heat medium detected by the circulating heat medium temperature sensor 38, and control the switching means based on this amount of temperature change.

The switching means in the second embodiment is configured to include a pair of valves 82 and a three-way valve 36. However, the configuration of the switching means can be modified as appropriate. For example, a three-way valve may be used instead of the pair of valves 82. Also, for example, a pair of valves may be used instead of the three-way valve 36, or a thermostat or the like may be used.

In the second embodiment, the heater is a heating heat exchanger 80. However, the heater is not limited to a heat exchanger and may be, for example, a heater that heats a refrigerant.

In addition, in the second embodiment described above, a heat storage tank 70 is provided in the circulation pipe 30, but the heat storage tank 70 can be omitted as appropriate.

(Modifications of the first and second embodiments)
Next, modified examples of the first embodiment and the second embodiment will be described. Note that, although various modified examples will be described below using the first embodiment as an example, these modified examples can also be appropriately applied to the second embodiment.

In the first embodiment described above, hot water is circulated between the heat pump 50 and the utilization facility 10 via the hot water supply header 22 and the hot water return header 28, etc. However, the configuration of the hot water supply header 22 and the hot water return header 28, etc. can be changed as appropriate.

In the first embodiment, the switching means is controlled by the CPU 100. However, for example, the operator may control the switching means using an operation button or the like.

The heat recovery system 130 according to the first embodiment heats up the low-temperature exhaust heat (low-temperature waste heat) recovered from the utilization equipment 10 using a heat pump 50 and supplies it back to the utilization equipment 10. However, the heat recovery system 20 according to the first embodiment may heat up the low-temperature exhaust heat (low-temperature waste heat) recovered from the utilization equipment 10 using a heat pump 50 and supply it to a utilization facility other than the utilization equipment 10.

In addition, the heat source of the heat source side heat exchanger 40 and the utilization equipment 10 are not limited to production equipment in the manufacturing industry, etc., and may be other equipment, etc.

Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and one embodiment and various modified examples may be used in appropriate combination, and the present invention may of course be embodied in various forms without departing from the spirit of the present invention.

10 Equipment used (heat source)
20 Heat recovery system 30 Circulation pipe 38 Circulating heat medium temperature sensor (second temperature detection unit)
40 Heat source side heat exchanger 50 Heat pump (use side heat exchanger)
70 Heat storage tank 72 Temperature sensor for stored heat medium (first temperature detection unit)
102 CPU (control unit)
130 Heat recovery system BP1 First startup bypass piping (First bypass piping)
BP2 Second startup bypass piping (second bypass piping)
V1 First start-up valve V1 (switching means)
V2 Second start-up valve V1 (switching means)
VH valve (switching means)

Claims (2)

a heat source side heat exchanger that exchanges heat generated by the heat source with a heat medium;
a utilization-side heat exchanger to which the heat medium is supplied from the heat source-side heat exchanger;
a heat storage tank that stores the heat medium supplied from the heat source side heat exchanger to the utilization side heat exchanger;
a switching means for switching between an operation mode in which the heat medium is circulated between the heat source side heat exchanger, the heat storage tank, and the utilization side heat exchanger, and a start-up mode in which the heat medium is circulated between the heat source side heat exchanger and the heat storage tank, bypassing the utilization side heat exchanger;
a circulation pipe for circulating the heat medium among the heat source side heat exchanger, the heat storage tank, and the utilization side heat exchanger;
a first bypass pipe that bypasses the utilization side heat exchanger and connects the downstream side of the heat storage tank in the circulation pipe to the downstream side of the utilization side heat exchanger;
a second bypass pipe that bypasses the utilization side heat exchanger and connects the downstream side of the heat storage tank and the downstream side of the utilization side heat exchanger in the circulation pipe, on the utilization side heat exchanger side of the first bypass pipe;
Equipped with
The switching means, in the start-up mode, causes the first bypass piping to bypass the utilization side heat exchanger, and then causes the second bypass piping to bypass the utilization side heat exchanger.
Heat recovery system. A first temperature detection unit that detects the temperature of the heat medium in the heat storage tank;
a second temperature detection unit that detects a temperature of the heat medium supplied from the heat storage tank to the utilization side heat exchanger;
A control unit that controls the switching means so that the start-up mode is selected when the temperature of the heat medium detected by the first temperature detection unit is less than a reference value, and the operation mode is selected when the temperature of the heat medium detected by the second temperature detection unit is equal to or greater than a reference value;
The heat recovery system of claim 1 .